Study of high strain rate effect on sheet formability based on Nakazima test

2017 ◽  
Author(s):  
Edoardo Mancini ◽  
Gianluca Chiappini ◽  
Archimede Forcellese ◽  
Marco Sasso ◽  
Michela Simoncini
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Sheet Formability

scholarly journals High strain rate effect on tensile ductility and fracture of AM fabricated Inconel 718 with voided microstructures

2021 ◽  
pp. 109908
Author(s):  
P Wood ◽  
A Rusinek ◽  
P Platek ◽  
J Janiszewski ◽  
J Sienkiewicz ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Inconel 718 ◽  
High Strain ◽  
Tensile Ductility ◽  
Strain Rate Effect ◽  
Rate Effect

Curvature Ductility of Concrete Element under High Strain-Rates

2012 ◽  
Vol 166-169 ◽  
pp. 2910-2917 ◽  
Author(s):  
Zubair Syed ◽  
Priyan Mendis ◽  
Nelson Lam ◽  
Tuan D. Ngo
Keyword(s):  
Strain Rate ◽  
Material Properties ◽  
Static Load ◽  
High Strain ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strain Rates ◽  
Material Models ◽  
Curvature Ductility ◽  
Concrete Elements

Considerable amount of studies on the ductility and flexural behaviour of normal and high strength concrete elements under static load can be found in literature. However, most of the previous theoretical investigations on moment-curvature (M-φ) relationship of concrete elements to calculate curvature ductility and flexural capacity did not take account of the strain-rate effect on the material models. M-φ analysis of concrete elements under dynamic loading are often conducted with material models developed for quasi-static load by applying Dynamic Increase Factors (DIF) to the material properties to reflect the strain-rate effect. Depending on magnitude and duration of applied dynamic load, element stiffness and boundary condition strain-rate varies over the cross section. Thus, the application of DIF to modify peak material properties often fails to reflect the strain-rate effect reliably. The improvement of using material model which incorporated strain-rate in its constitutive equations has been explored in this study. The effects of reinforcement amount, grade and concrete strength on curvature ductility for different strain rates have been studied using material models which have strain-rate effects included in theirs formulation. Based on the parametric study, a simple formula to estimate curvature ductility for concrete elements under explosive loads (high strain-rates) has been proposed.

scholarly journals Strain-rate effects associated with the HJC concrete model

2018 ◽  
Vol 183 ◽  
pp. 01008 ◽  
Author(s):  
Gordon Johnson ◽  
Timothy Holmquist ◽  
Charles Gerlach
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
Confining Pressure ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Published Data ◽  
Strain Rate Effects ◽  
Third Invariant ◽  
Rate Effects ◽  
Additive Term

The Holmquist-Johnson-Cook (HJC) model for concrete was presented in 1993 and has been used extensively since that time. Since then a third invariant effect has been added and the shear modulus has been revised to vary such that Poisson's ratio is held constant. It has always been diffcult, however, to determine the appropriate constant for the strain-rate effect as most of the published data are for the net stress as a function of the strain rate. Because concrete is both pressure dependent and strain-rate dependent, it is necessary to separate the individual effects. Recently strain-rate data for three concrete materials were presented by Piotrowska and others [1, 2], where the data are presented as equivalent stress versus confining pressure for a high strain rate and a quasi-static strain rate. This is the form necessary to determine the appropriate strain-rate effect, and the data show that the strain-rate effect is larger than used in the initial publication of the HJC model, and also that the strain-rate effect is a function of the confining pressure. For lower pressures the strain-rate effect is a factor to be applied to the quasi-static data (which is the effect represented in the original HJC model), but for higher pressures the strain rate effect is better represented by an additive term. With the addition of an another HJC constant (the pressure at which the strain rate effect transitions from a multiplied factor to an additive term) it is possible to more accurately represent the response of concrete under high pressures and high strain rates, and it is possible to compute more accurate results for projectile penetration into concrete targets. The paper presents the modified form of the HJC model, an analysis of the strain-rate effects, and results of penetration computations that are compared to experimental data in the literature.

scholarly journals Strain Rate Effect on Acoustic Emission Characteristics and Energy Mechanisms of Karst Limestone under Uniaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Qingsong Wang ◽  
Jianxun Chen ◽  
Jiaqi Guo ◽  
Yanbin Luo ◽  
Yao Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Strain Rate ◽  
Uniaxial Compression ◽  
Strain Energy ◽  
High Strain ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strain Rates ◽  
High Strain Rates ◽  
Ae Signals

In this paper, the strain rate effect on mechanical properties, failure modes, acoustic emission (AE) characteristics, and energy mechanism of the karst limestone was analyzed based on uniaxial compression tests with different strain rates (5 × 10−6–5 × 10−4/s). The results showed that the peak strength increased linearly and peak strain increased quadratically with the logarithm value of the strain rate. Moreover, the strain rate effect on elastic modulus was not significant. Under low strain rates, the rock was damaged seriously, AE signals appeared continuously, and the cumulative number of AE signals was high. Under high strain rates, the total quantity of the macroscopic cracks decreased, but the crack length extended with better coalescence. The AE peak significantly increased under high strain rates, while the cumulative AE activity significantly reduced. The energy evolution of the karst limestone failure process had significant stage characteristics, and the strain energy ratio presented an S-shape. The maximum value of the elastic strain energy at peak stress showed a linear relationship with the logarithm value of the strain rate.

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